Countercurrent treatment of hydrocarbon oil



March 21, 1939. Q ROBERTS I 2,151,529

COUNTERCURRENT TREATMENT OF HYDROCARBON OIL Filed June 10, 1933 [nven for Oscar L. Roberls y/ Qg /44 Ailorney Patented Mar. 21, 1939 COUNTEROURRENT TREATMENT or HYDROCARBON OIL Oscar L. Roberts, Ardmore, Pa., assignor to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania Application June 10, 1933, Serial No. 675,250

12 Claims.

The present invention relates to a process for obtaining countercurrent contact between partially immiscible liquids, and particularly to the extraction of components from hydrocarbon oils with a'solvent which will selectively dissolve such components. This invention is particularly ap-' plicable to the separation of highly naphthenic or asphaltic oils into fractions respectively more parafflnic and more napthenic than the original oil.

Heretofore, it has been found that certain selective solvents, as for example, nitrobenzene, phenol, aniline and others, may be used to effect a separation of hydrocarbon oils, such as petroleum, into fractions of substantially the same boiling range but of different chemical compositions and of different physical properties. The difference in physical properties of the fractions so produced, i. e., the degree of paraifinicity or naphthenicity of the said fractions, may be expressed by the relationship of viscosity to gravity for any particular oil. The viscosity-gravity constant, as developed by Hill and Coats, referred to in Industrial and Engineering Chemistry, vol. 20, page 641 (1928) will be used herein to indicate the degree of paraflinicity or naphthem'city of the oil or oil fractions; the lower the value for the constant, the higher the degree of parafiinicity of the oil.

In the process of extracting hydrocarbon oils,

I have found that for a given temperature and ratio of solvent to oil, the percentage of oil which appears as the naphthenic portion compared to that which appears as the paraffinic portion is dependent upon the relative quantities of naphthenic and paraflinic constituents present in the original oil.

Furthermore, I -have found that by adding paraflinic oil to the charging stock, thereby increasing the paraflinic content of the same, I effect a beneficial change in the distribution 00- efliclent of the oil during the extraction process. By so increasing the paraiiinicity of the charging stock or of the oil undergoing treatment in any stage of the extraction system, I am able to produce a larger yield of parafilnic oil of given viscosity-gravity constant or the same yield of paraflinic oil of lower viscosity-gravity constant, than could have been produced without enrichment of the charging stock or without increasing the ratio of solvent to stock. Moreover, I have been able to simultaneously reduce the refrigeration necessary to efiect a separation of undissolved oil from solvent containing oil dissolved therein, since the degree of cooling required to cause separation is dependent upon the paraflinicity or naphthenicity of the oil being extracted; paraflinic oils have a higher miscibility temperature than naphthenic. oils and therefore require less cooling to effect separation.

Briefly, my process comprises first intimately contacting a selective solvent and a hydrocarbon oil, thereby to effect solution of a portion of the oil in the selective solvent, then separating the undissolved oil from the solvent and oil dissolved therein, and adding at least a portion of the said undissolved oil to the charging oil, whereby the .parafiinicity of the charging oil is increased to a substantial extent. My process may be carried on in'either a batch or continuous extraction system and the parafllnlc oil fraction may be withdrawn from and added to any desired stage of said system. I also contemplate, within the scope of my invention, the addition of paraifinic oil other than that produced by the extraction process, to the charging oil or to the oil at any stage in the extraction system. For example, naturally occurring paramnic oil or an undissolved oil fraction of increased parafllnicity produced by a separate extraction process, may be added to my charging oil or to the oil in any stage of my extraction system.

My invention is particularly well adapted to the extraction of markedly naphthenic or asphaltic oils, which stocks. present serious difliculties in conventional extraction processes. In the treatment of such stocks containing relatively small quantities of paraflinic constituents, it is impossible in some instances, to effect a separation of undissolved oil and solvent containing oil dissolved therein, except by chilling to extremely low temperatures. This economic difficulty may be obviated, -in part at least, by the addition of paraillnic oil to the naphthenic stock prior to extraction, and the parafilnic components of said stock may thereby be recovered.

For purposes of illustration, reference is made to the accompanying drawing, which shows diagrammatically, apparatus suitable for carrying on my process:

In the drawing, a series of alternate mixing vessels (I, 3, 5, and 'l) and settling vessels (2, 4, 6, and ,8) are located in step-like arrangement, the mixing vessels being provided respectively with paddle stirrers (9, 9a, 9b, and 9c) "'or other suitable mixing devices, and means for introducing thereinto oil and solvent, and means for passing the mixture therefrom into the settling chambers. The settling chambers are provided with means for passing undissolved oil, to succeeding and solvent to preceding mixing chambers. There is also provided means for recycling undissolved oil from the last settling chamber to any desired mixing chamber. The system of low pressure pumps, feed pipes and heat exchangers, is so arranged as to maintain a, regulated countercurrent flow of oil and solvent thru the extraction stages, the heat exchangers (I2, I6, 28, 35, and

. 4|) serving to control the temperatures of the oil and solvent streams, and thus indirectly the temperatures of the materials in the mixing and settling vessels.

In the operation of my process, I may choose. for example, nitrobenzene as the selective solvent, and a lubricating oil as thestock to be selectively extracted. The oilstock supplied from a storage tank (not shown) is drawn through valve controlled pipe III by means of pump l I, and is passed thru cooler l2 and pipe [3 into mixin vessel l. The selective solvent, 1. e., nitrobenzene, is conducted from a supply tank (not shown) through valve controlled line 39, and is passed by means of pump 40 through heat exchanger 4i and pipe 42 into mixing vessel 1. After suilicient oil and solvent has been supplied to the system, a continuous countercurrent flow will be set up, and the extraction process will commence to function. The oil stock is charged to mixing vessel l, and the partially spent solvent from the bottom of settler 4 which flows through pipe 20, valve l9 and pipe I8, is forced by pump I! through cooler l6 and pipe l into mixing vessel I, wherein said oil and solvent are thoroughly contacted by the stirrer 9. The mixture flows by gravity from the bottom of vessel I, through pipe l4 into settling vessel 2, and a separation of undissolved oil and solvent containing dissolved oil is effected by the difference in gravity, the undissolved 011 comprising the upper layer and the solvent the lower layer. The spent solvent, having passed thru four extraction stages, is drawn from the bottom of settler 2 through valve controlled-line 2| to storage, prior to separation of solvent from dissolved oil, as by vacuum distillation. The undissolved oil layer, containing a small quantity of solvent, occupies the upper portion of settler 2, and flows by grav- 24, valve 25, pipe 28, pump 21, heat exchanger 28,.

and pipe 29. The oil and solvent are herein again thoroughly contacted by stirrer 9a and the mixture flows from the bottom of the mixing vessel 8 thru pipe 23 into settler 4 where the separation of undissolved oil and solvent layers is eilected. The lower solvent layer is withdrawn from settler 4 through pipe 20, and is pumped to mixing vessel I, ashereinbefore described. The undissolved oil layer in the upper portion of settler 4 is passed by means of pipe 50 into mixing vessel 5 and at the same time relatively fresh solvent from the bottom of settler 8 is withdrawn thru pipe 32, valve 33, and pipe "a, and forced by pump 34 thru heat exchanger 55 and pipe 36 into mixing .veuel 5. The contacting process is again effected in mixing vessel 5 by means of stirrer 9b, the mixture flowing from the bottom of said vessel thru pipe 5| into settler 5, wherein separation of undissolved oil and solvent layer is. effected, the solvent being drawn from the bottom of the settler and passed to the preceding mixing vessel 3. The undissolved oil layer from settler 6 is passed into mixing vessel 1 by means of pipe 31, and simultaneously there is added fresh solvent from stor age (not shown), said solvent being drawn from valve controlled line 39 by pump 40, and passed thru heat exchanger 4| and pipe 42 into the mixing vessel 1. Intimate contacting of the oil and fresh solvent is eifected by stirrer 9c and the mixture is drawn from the bottom of vessel 1 through pipe 34 into settler 4. Herein a separation of undissolved oil and solvent layers is effected, the undissolved parafllnic oil being drawn from the top of the settler I thru pipe 4!, and the solvent and oil dissolved therein is pumped from the bottom oi said settler by pump 34, and is delivered to mixing vessel 5 for further-use. In this system, it will be seen that by the countercurrent contacting the undissolved oil becomes increasingly parafflnic and the solvent becomes more and more saturated with the naphthenic components oi the oil undergoing extraction. Normally, the temperatures maintained in the successive stages are higher as the oil becomes more paramnic, i. e., the first stage operates at the lowest temperature and the last stage at the highest temperature, the intermediate stages operating at temperatures intermediate the highest and lowest.

The paraflinieoil layer which contains a small quantity of solvent is withdrawn from settler 8 by means of pipe 43, and any desired portion may be removed from the system through valve controlled line 44. The remainder of said paraiiinic fraction is passed by means of valve 45 and pipe 46 to pump 41, which forces the oil thru heat exchanger 48 into pipe 49. In order to increase the paraifinicity of the charging oil or the oil in any intermediate stage, a quantity of the paraflinic oil may be passed thru line 49 and valve 59 into admixture with the charging oil in line l3, or said parafllnic oil may be introduced into any desired stage, as for example, into mixing vessel 3 by means of pipe 56, valve 51, and pipe 58. The oil from the second or third stages may be likewise rendered more parafllnic by introducing oil from pipe 49 respectively into mixing vessels 5 or I by means of pipe 53, valve 54 and pipe 55, or pipe 50, valve 5| and pipe 52. By thus increasing the percentage of paramnic constituents in the oil charged to the first or intermediate stages, a higher yield of paraflinic oil of lower viscosity-gravity constant may be obtained from the extraction system.

Furthermore, I may effect an increase in parafllnic components of the oil delivered to the first or intermediate stages of the system by adding a portion of the undissolved oil from any stage to one or more of the preceding stages, 1. e., a portion of the undissolved oil from the third stage settler may be introduced into the mixing vessels of the second and/or first stages.

While I have illustrated my process by means of a 4-stage countercurrent extraction apparatus, I do not intend to limit myself thereto, but may employ any system of one or more stages, operable either in batch or continuous manner.

As a further example of my process, a high viscosity distillate from a ,Texas crude oil was treated with 250% of nitrobenzene in a 3-stage batch countercurrent extraction apparatus. Oi. the paramnic oil fraction removed from the last stage, was recycled and mixed with the fresh oil entering the 1st extraction stage. A comparison of the yield of parafiinic oil obtained by operating in this manner, with the yield when no recycling was used, is as follows:

In the appended claims, the term "viscous hydrocarbon oil" is tobe understood to comprehend oils having a Saybolt Universal viscosity at 100 F. of 50 seconds or more.

What I claim is:

l. A process for extracting a viscous hydrocarbon oil with a selective solvent, which comprises intimately contacting said oil and solvent in a mixing zone, passing the oilesolvent mixture therefrom into a settlingzone, separating the undissolved oil from the solvent and oil dissolved therein, and passing at least a portion of said undissolved oil into the said mixing zone, in contact with the oil and solvent being admixed therein.

2. A process for extracting a viscous hydrocarbon oil with a selective solvent, which comprises intimately contacting said oil and solvent in a mixing zone, passing the oil-solvent mixture therefrom into a settling zone, separating the undissolved oil from the solvent and oil dissolved therein, passing at least a portion of said undissolved oil into said mixing zone in contact with the oil and solvent being admixed therein, and withdrawing solvent and oil dissolved therein from said settling zone.

3. A process for continuously extracting a viscous hydrocarbon oil with a selective solvent, which comprises passing the oil and solvent in countercurrent contact with each other through at least two extraction stages, separating the undissolved oil from the solvent and oil dissolved therein, and recycling at least a portion of said undissolved oil to the mixing zone of a preceding extraction stage, in contact with the oil and solvent being admixed therein.

4. A process for continuously extracting a viscous hydrocarbon oil witha selective solvent, which comprises passing the oil and solvent in countercurrent contact with each other through at least one extraction stage, separating the undissolved oil from the solvent and oil dissolved therein, and recycling at least a portion of said undissolved oil to the mixing zone of the extraction stage from which it was withdrawn, in contact with the oil and solvent being admixed therein.

5. A process for continuously extracting a viscous hydrocarbon oil with a selective solvent, which comprises passing the oil and solvent in countercurrent contact'with each other through a plurality of extraction stages, each comprising a mixing zone and a settling zone separating the undissolved oil from the solvent and oil dissolved therein, and recycling at least a portion of said undissolved oil to the mixing zone or a preceding extraction stage, in contact with the oil and solvent being admixed therein.

6. A process for continuously extracting a viscous hydrocarbon oil with a selective solvent, which comprises passing the oil and solvent in countercurrent contact with each other through a. plurality of extraction stages each comprising a mixing zone and a settling zone, separating the undissolved oil from the solvent and oil dissolved therein, and recycling at least a portion of said undissolved oil to the mixing zone of the extraction stage from which it was withdrawn, in contact with the oil and solvent being admixed therein.

7. A process for continuously extracting a viscous hydrocarbon oil with a selective solvent, which comprises passing the oil and solvent in countercurrent contact with each other through a plurality of extraction stages each comprising a mixing zone and a settling zone, continuously separating the undissolved oil from the solvent and oil dissolved therein, and passing at least a portion of said undissolved oil and solvent containing oil dissolved therein to the mixing zone of a preceding extraction stage, in contact with the oil and solvent being admixed.

8. A process for continuously extracting a viscous hydrocarbon oil with a selective solvent, which comprises passing the oil and solvent in countercurrent contact with each other through a plurality of extraction stages each comprising 'a mixing zone and a settling zone, continuously separating the undissolved oil from the solvent and oil dissolved therein, recycling at least a portion of said undissolved oil to the mixing zone of the same stage from which it was withdrawn, in contact with the oil and solvent being admixed therein, and passing the solvent and oil dissolved therein to the mixing zone of a preceding extraction stage, in contact with the oil and solvent being admixed therein.

. 9. A process for continuously extracting a viscous hydrocarbon oil with a selective solvent, which comprises passing the oil and solvent in countercurrent contact with each other through a plurality of extraction stages each comprising a mixing zone and a settling zone, continuously separating the undissolved oil from the solvent and oil dissolved therein, and passing at least a portion of said undissolved oil from the settling zone of the last stage to the mixing zone of a preceding extraction stage, in contact with the oil and solvent being admixed therein.

10. A process for the separation of a hydrocarbon oil mixture into fractions relatively more parafiinic and fractions relatively less parafilnic in character than the original hydrocarbon oil mixture which comprises admixing said hydrocarbon mixture with oil which is relatively more parafilnic in character than said hydrocarbon oil mixture and further characterized by containing a substantial proportion of oil fractions having the same boiling range as the oil fractions contained in the hydrocarbon oil mixture and thereby increasing the ratio of paraflinic fractions to nonparamnic fractions in said mixture, commingling the hydrocarbon oil mixture which has been admixed with said relatively more paraflinic oil with a selective solvent and thereby forming an extract phase and a rafflnate phase and separating said phases.

11. A process asclaimed in claim 10 in which the oil admixed with the hydrocarbon mixture an oil which has previously been extracted with a selective solvent.

12. In a process for. continuously extracting a viscous hydrocarbon oil mixture with a selective solvent wherein the solvent and hydrocarbon oil mixture are passed in countercurrent contact with each other through a plurality of extraction stages, the step which comprises admixing with the hydrocarbon oil mixture undergoing extraction in any stage, a second viscous oil which is relatively more paraiiinic in character than said hydrocarbon oil mixture and further characterized by containing a substantial proportion of oil components having substantially the same boiling range as the oil components in the. hydrocarbon oil mixture, thereby to increase the ratio of parafilnic components to non-paraflinic components in said admixture undergoing extraction in that stage.

OSCAR L. ROBERTS. 

